This invention is concerned with improvements relating to the manufacture of air pillows, in particular air pillows of thin-walled plastic sheet which may be used as an infill or cushioning in the packaging and transportation of fragile articles.
Conventionally utilised in the manufacture of air-filled pillows is thin walled polythene tubing, which may be unwound from a continuous supply thereof flat-wound on a reel, and it is in this context that the invention will hereinafter be described, although it is to be appreciated that the invention is not limited to the use of polythene as such, and that other appropriate materials may be utilised as desired.
Numerous suggestions have been made for the manufacture of air-filled pillows of this kind (hereinafter referred to as being of the kind specified), but in general difficulty has been encountered in the injection of air into a section of tubing, and subsequently sealing the tube to form individual pillows.
According to this invention there is provided a machine for the manufacture of air-filled pillows comprising:
a) a separator member which may be inserted into a length of plastic tubing drawn from a supply thereof;
b) retaining means for retaining the separator member in a desired position in the machine, within the tubing, in such a manner as to allow the tubing to be pulled across the separator member;
c) an injector means co-operable with the separator member to inject air through one wall of the tubing into the interior of the tubing; and
d) sealing means to seal the tube across the location of the injection point.
By the use of a separator member which is captive within the polythene tubing to separate the walls of the tubing, injection of air through an aperture in the tubing may more reliably be accomplished without the risk of puncturing the tubing at two locations. Specifically by the use of the separator member, such injection may be accomplished without the need for air pressure within the machine to hold the walls of the tube apart, whilst injection is taking place.
Preferably the separator member additionally provides a supporting surface to support one wall of the tubing whilst an injection nozzle is inserted through the wall, during the injection of air into the space between the walls of the tubing.
Preferably the machine comprises drive means to draw tubing material from the supply thereof, conveniently by intermittent operation.
Preferably the machine comprises control means for the injector means, the drive means and the sealing means, which is operative to cause the injector means to operate whilst operation of the drive means is momentarily terminated, and subsequent to operation of the injector means to cause the drive means to advance the material a short distance to the sealing means.
Preferably the machine comprises a support member located adjacent to the separator member and between which one wall of the tube is located as the tube is advanced through the machine, and conveniently the support member is provided with an aperture in alignment with an aperture provided in the separator member, through which a nozzle of the injector means passes in the injection of air into the tube.
The retaining means for the separator member may be provided by a housing in which part of the separator member is located in a manner such as to prevent any substantial movement of the separator member from a desired position within the machine, particularly as tends to occur as the tubing is drawn over the separator member in the operation of the machine, but such as to allow the polythene tubing to be drawn through the housing over the separator member as the tubing is advanced through the machine.
Conveniently the housing is split, comprising portions which may be secured together so as to extend partially at least around the separator member whilst within the tube.
Alternatively the retaining means may be provided by one or more drive rollers of the machine with which the separator member is drawn into engagement as the drive means operates to draw tubing through the machine.
Preferably the sealing means is operative to seal the tube along two lines extending transversely of the tube on opposite sides of the injection point, and to provide a tear-line extending between the two seal lines.
According to this invention there is also provided a machine for the manufacture for air-filled pillows from a continuous supply of plastic tube flat-wound onto a reel, the machine comprising
a) a drive assembly to advance the plastic tube intermittently through the machine;
b) injection means operative intermittently to inject air into the space between upper and lower walls of the tube; and
c) sealing means operative downstream of the injection means intermittently to seal the upper and lower walls of the tube; characterised in that
a separator member is provided which is located within the tube between the upper and lower walls thereof upstream of the injection means, said separator member being maintained in an operative position within the machine during advancement of the tube through the machine by engagement with the drive assembly.
Conveniently said engagement is indirect, in the sense that the separator member engages the drive assembly through the thickness of the polythene tube.
Conveniently the drive assembly engages the tube to draw the tube over the separator member whilst preventing substantial movement of the separator member from a desired position relative to the machine.
Preferably the drive assembly comprises upper and lower rollers operative to engage the upper and lower walls of the tube.
Advantageously the separator member is adapted to co-operate with the injector means, and comprises an aperture through which a nozzle of the injector means passes in the injection of air into the space between the upper and lower walls of the tube.
According to this invention there is also provided a method of making an air-filled pillow involving the use of continuous thin-walled plastic tube, in which the walls of the tube are retained apart by a separator member which is retained in position whilst the plastic film is drawn from a supply thereof, the separator member retaining the walls of the tube separated during the injection of air into the tube.